Overexpressing Fragments of CREB-Binding Protein (CBP) to Block Transcriptional Dysregulation and Toxicity in Huntington's Disease
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Huntington’s disease (HD) is caused by expression of the huntingtin gene containing an expanded CAG repeat. N-terminal mutant huntingtin protein (N-mHtt) accumulates in the nucleus and impairs transcription of a subset of genes through incorporation into transcriptional complexes or sequestration of proteins away from the promoter. CREB-binding protein (CBP) is a transcriptional co-activator and acetyltransferase (AT) that binds to N-mHtt. We hypothesized that overexpressing CBP fragments that lack a promoter association domain would block N-mHtt-mediated transcriptional dysregulation and toxicity. We found that overexpressing full-length CBP or CBP fragments did not reverse transcriptional dysregulation, but did decrease toxicity in a cell model of HD. Overexpressing fragments of CBP containing the AT domain increased toxicity in wild-type cells, while overexpressing a fragment lacking this domain had no effect. We conclude that excess AT activity was detrimental in wild-type cells, while overexpressing CBP or CBP fragments was protective in HD cells.